1. Field of the Invention
This invention relates to a method and apparatus for optically checking the appearances of chip-type electric or electronic components (e.g., chip-type capacitors, core components such as coils and the like, LC multiple components, and the like) and carrying out sorting of the chip-type components.
If a component of this type has any imperfection or defect in its exterior, for example, an unusual shape, dimensional errors, breakage, cracks and the like, such defect may badly affect the characteristics of the component and may bring about any trouble in the mounting of the component on a substrate. Therefore, it is necessary to check the appearances of components as well as the characteristics of the components.
2. Description of the Prior Art
Previously, the appearances of chip-type components were visually inspected by the naked eye or using a magnifying lens or the like.
Referring now to FIGS. 1(a) to 1(c), one of conventional methods of checking the appearances of chip-type components will be described in order to facilitate understanding of the present invention.
In FIG. 1(a), a reference numeral 10 designates a chip storage box in which a plurality of chip-type components 20 are received, and a reference numeral 11 designates a first glass pallet. In FIG. 1(b), a reference numeral 12 designates a stanchion extending upward from a base 13 and a reference numeral 14 designates a magnifying lens held by a horizontal supporting bar 15 which is supported to an upper end portion of the stanchion 12. First, chip-type components 20 are taken out of the storage box 10 by a spoon 16 to be placed on the first glass pallet 11 in a manner not to overlap one another as shown in FIG. 1(a). Secondly, the first glass pallet 11 having the chip-type components 20 put thereon is placed on the base 13. Then, a top surface side of each of the chip-type components 20 put on the first glass pallet 11 is subjected to visual inspection while each of the chip-type components 20 is magnified by the magnifying lens 14. When chip-type components having any defects in their exteriors are found through the visual inspection, the defective components 20' are picked up an collected in a waste box 17 as shown in FIG. 1(b). After the defective components 20' are all removed from the first glass pallet 11, a second glass pallet 18 is superposed on the first glass pallet 11. Then, the superposition of the first and second glass pallets 11, 18 is reversed as shown in FIG. 1(c), whereby the remaining chip-type components which were till now on the first pallet 11 shift to the second glass pallet 18 with the undersurface sides of the chip-type components facing upward. The first glass pallet 11 is removed from the second glass pallet 18 and the second glass pallet 18 is placed on the base 13. Then, the above-described procedure is substantially repeated to visually check the undersurface sides of the chip-type components on the second glass pallet 18. Thus, acceptable chip-type components are classified and sorted out from defective chip-type components.
With this conventional method, since the appearances of chip-type components are visually inspected through the magnifying lens by an inspector as described above, the checking operation typically depends on the individual inspector, so that it is impossible to set a uniform criterion for inspecting the appearances of chip-type components. In other words, criteria for inspecting the appearances of chip-type components generally vary from one field inspector to another field inspector. Therefore, chip-type components appreciated as acceptable components through the visual inspection of field inspectors may differ from one another in quality. In addition, in the conventional method, the placing of chip-type components on the first glass pallet, classifying of defective components from acceptable components, and the like are all manually carried out, so that a checking accuracy may be decreased due to an inspector fatigue, a human-caused mistake and an inspector's mood of the moment. In order to increase the checking accuracy, it is necessary to increase the number of inspectors who take charge of the checking of chip-type components. This makes chip-type components too expensive.